In motor vehicles it is possible to select, activate or deactivate a large number of control functions or on and off switching commands for various types of components by way of actuating elements. Thus it is usual, for example, to control, raise, lower or to open and close the windows, sunroof, exterior mirrors or similar by means of electrically operated positioning motors. Furthermore, a large number of function switches are provided in motor vehicles by way of which the electrical consumers, such as heating, ventilation, lighting elements, radio, on-board computer, navigation system and similar can be operated.
The actuating elements for such functional agents in motor vehicles are usually mounted in the central console, the dashboard and/or on the steering wheel.
The various actuating elements are designed not merely from the point of view of an advantageous mode of operation but must also have an advantageous appearance and surface feel. To this end it is usual, especially in the area of the dashboard and the steering wheel, for the actuating elements to be disposed within a decorative layer. In this case, by making an electrical contact in the conventional manner, the actuating elements activate a control device, which controls the individual positioning motors for the functional agents.
The actuating elements are mostly disposed in the decorative layer in the form of pushbuttons so that they are raised perceptibly proud of the surface. However, this tangible arrangement of the actuating elements means that the decorative layer must be of interrupted design in the area of said actuating elements. Conversely this leads, especially in the area of transitions from the decorative layer to the individual actuating elements, to the creation of joints in which dirt collects over time, which can impair both the mode of operation of the actuating elements and also the appearance of the whole decorative layer.
According to the applicant's knowledge, the problems referred to above can be eliminated by the use of piezoelectric actuating elements instead of the conventional actuating elements. In this case the decorative layer can be designed as substantially closed, whereby a piezoelectric element is disposed underneath the actuating elements represented visually on the decorative layer. This piezoelectric element is advantageously a piezoelectric film.
Piezoelectric switches, for example for Ceran cooker tops, coffee machines or “vandal-proof” keypads, are known for instance from DE 69 304 443 T2. This printed matter also discloses the method of production for a piezoelectric film or piezo film so that the production of a piezo film can essentially be considered as known to a person of ordinary skill in the art. Thus a precise description of the production of a piezo film is omitted in the following. However, it should be noted that in the production of a piezo film, a piezoelectric varnish and insulating layers are generally applied to a base material by means of a screen printing technique.
Nowadays switches and actuating elements of all types in the vehicle must be illuminated so that they can be found effortlessly even in the dark. In this case a distinction is made between pilot lighting and functional lighting.
Functional lighting serves to display an activity and must also be visible by day. This is mostly achieved by means of LEDs or light bulbs. Pilot lighting serves to determine the position of individual switches at night. This can occur in a motor vehicle in different ways and means, e.g. by indirect illumination of the whole switch surface, backlighting of an individual switch (by light bulbs) or of the whole switch surface (e.g. by a luminescent film) or also by low-energy luminescent light-emitting diodes adjacent to them.
The use of light bulbs, however, is eliminated for piezoelectric technology. Furthermore, the applicant's investigations have shown it to be advantageous to use a luminescent film in conjunction with piezoelectric switches or piezoelectric actuating elements. The production of a luminescent film is generally known to a person of ordinary skill in the art, whereby a luminescent material is applied as a rule together with electrodes to a base material by means of a screen printing technique.
Based on the explanations referred to above, the applicant came to the conclusion that a combination of piezo film and luminescent film is advantageous for the production of an actuating element for a vehicle, which simultaneously solves the problems of the prior art and can additionally be provided easily with pilot lighting.
Up to now this combined piezo/luminescent film has been produced in such a way that piezo films and luminescent films are produced independently of each other. For example, a piezo film is produced according to the disclosure of DE 69 304 43 T2 and a luminescent film as is described for example in DE 102 55 199 A1. The two piezo films and luminescent films produced independently of each other are preferably bonded by gluing the individual elements together in order to produce a laminate.